Preferential transport of microplastics by wind

Contamination of terrestrial and marine environments by plastic waste has been widely documented. Most research into the distribution of microplastics has focused on water but here we show that wind transport can be very effective in mobilising microplastic particles. A series of wind tunnel experiments using two different substrates (sand and soil), two different microplastics (microbeads and fibres) and 5 different concentrations of microplastics (ranging from 0 mg kg-1dw to 1040 mg kg-1dw) is used to demonstrate that microplastics are preferentially transported by wind compared to sand and soil. When compared to either of the untreated substrate beds (0 mg kg-1dw), the inclusion of microplastics was not found to significantly affect the wind erosion threshold for any of the concentrations or geometric forms (fibres or beads) tested. Averaged over all concentrations of microplastics and both substrate types, microplastic enrichment was lower for microbeads than fibres. The enrichment of microplastic fibres within the entrained particulate matter was one to two orders of magnitude higher for both test bed substrates, ranging from 98 to 498 for the sand and 278 to 726 for the soil. This suggests microplastic shape needs to be carefully parameterized in models of atmospheric microplastic transport. We suggest that microplastic research could benefit from previous investigations into the wind erosion of soil organic carbon.